Swage fasteners with a high stand-off collar

ABSTRACT

A swage type fastener including a pin and a collar adapted to be swaged onto the pin by the application of a relative axial force by an installaiton tool, with the pin having a lockgroove portion, a tubular collar having an inner and outer end and adapted to be located on the pin and having a collar shank portion adapted to be swaged into the lock groove portion by the relative axial force applied between the pin and the outer end of the collar by the installation tool, the collar having a through bore which has a reduced diameter bore portion whereby the collar is generally piloted on the pin, and the collar shank portion being generally frusto conically shaped from the reduced diameter bore portion to an enlarged bore portion at the outer end, the collar shank portion having a generally uniform wall thickness from the outer end for a distance over its swageable length whereby the frusto conical shape of the collar shank portion provides a high hold-off to resist initiation of swage of the outer end of the collar into the locking grooves of the pin and whereby the generally uniform wall thickness provides for a generally uniform fill of the lock groove portion substantially without distortion.

This is a division of U.S. Pat. application Ser. No. 362/738, filed June7, 1989, now U.S. Pat. No. 4,921,384.

SUMMARY BACKGROUND OF THE INVENTION

The present invention relates to multi-piece fasteners and moreparticularly to a swage type fastener for clamping workpieces togetherunder a high initial pre-load prior to initiation of swage.

The present invention generally relates to two-piece swage typefasteners or lockbolts of the type illustrated in U.S. Pat. No.3,915,053 to J. Ruhl, issued Oct. 28, 1975, U.S. Pat. No. 2,531,048 toL. Huck, issued Nov. 21, 1950 and to U.S. Pat. No. 3,057,246 to H. G.Brilmyer, issued on Oct. 9, 1962. The present invention is also animprovement upon U.S. Pat. application Ser. No. 282,875 by Richard D.Dixon for Variable Clamp Fastener and Method filed on Dec. 9, 1988issued on Sep. 19, 1989 as U.S. Pat. No. 4,867,625 and copending U.S.Pat. application Ser. No. 328,305 by Shahriar M. Sadri for Fit Up SwageFastener With A Variable And Selectively High Initial Clamp Pre-load AndMethod filed on Mar. 24, 1989. In addition the present invention couldutilize the groove shape and concepts of U.S. Pat. application Ser. No.185,327 by Richard D. Dixon for High Strength Fastener and Method filedon Apr. 20, 1988. All of the above patents and noted patent applicationsof Dixon (but not Sadri) can be considered as prior art relative to thepresent invention.

In one form, the fastener of the present invention, as with the priorart noted, includes a pin and a collar adapted to be swaged into lockgrooves in the pin in response to a preselected relative axial forceapplied between the pin and collar. In lockbolt type constructions, thecollar transmits an axial force from the swage anvil of the setting toolto the workpiece surface engaged by the collar. The pin transmits anopposite axial force by virtue of a pulling force exerted by the tool aswith a pull type fastener or a reaction force on the pin as with a stumptype fastener. The final clamp load on the workpieces can be determinedfirst by the initial magnitude of relative axial force before initiationof swaging the collar onto the pin and thereafter by elongation of thecollar in response to swage. The initial axial clamp force on theworkpieces is sometimes referred to as "pre-load" while the finalclamping force after full swage is referred to as "final clamp load".The beginning of swaging at this pre-load is sometimes referred to as"primary clinch". In many applications it is desirable to provide a highlevel of pre-load. In these cases the relative geometries of the swageanvil and engaging end of the collar are selected to provide hold-off orstand-off of initial swage until the desired pre-load value is attained.Thus U.S. Pat. No. 2,531,049 issued Nov. 21, 1950 to L. C. Huck shows acollar having a frangible flange to assist in stand-off of initiation ofswage. The companion U.S. Pat. No. 2,531,048 issued Nov. 21, 1950 to L.C. Huck shows a collar with an enlarged bead to assist in stand-off. Amodified form of collar and bead structure is shown in the U.S. Pat. No.2,804,798 issued Sept. 3, 1957 to H. G. Brilmyer. The beaded structuresprovide an increase in hoop strength by virtue of a localized area atthe front or outer end of the collar having an increased wall thicknessand hence increased volume of collar material.

One of the problems, however, with the provision of a bead on the collarfor increased stand-off is that the collar now has an unevendistribution of material over its length. This can result in unequalfilling of the pin lock grooves and, perhaps more importantly, couldresult in excessive collar material being moved radially inwardly intothe pin lock grooves resulting in local necking of the pin and potentialloss of overall strength of the set fastener. This problem is compoundedwhere the collar is swaged into lock grooves which are helical threads.Here it may be desirable to remove the collar by unthreading it from thepin. Excessive necking could distort the threads and severely inhibitsuch removal making disassembly of secured parts more difficult.

The present invention presents a unique response to the problem ofproviding a swage fastener having a high stand-off capability whileproviding generally equal groove fill in the pin and minimizinglocalized pin distortion. This is accomplished by constructing thecollar to be generally conically shaped over the portion to be swaged;thus the collar is of a generally uniform wall thickness with the insideand outside diameters increasing in an axial direction from the innerend to its enlarged outer end. The result is a relatively small butsignificant radial gap separating the inner surface at the outer end ofthe collar from the lock grooves; this radial separation along with theconical shape serves a purpose to be seen. At the same time, since thewall thickness of the collar is maintained generally uniform throughoutits swageable length, the volume of material available to be swaged intothe lock grooves of the pin will be generally the same across the swagearea. Thus a more uniform fill will be achieved while pin necking willbe minimized.

In some applications it may be desirable to provide a pin and collarcombination in which there is a predetermined amount of "overpack".Overpack occurs where the volume of collar material to be swaged in thepin lock grooves is greater than the available volume defined by theconfronting volume of the cavity of the swage anvil and the pin lockgrooves. The collar construction of the present invention provides for amore uniform overpack condition over its swageable length.

As can be seen from the prior art patents, the outer end of the collaris frequently provided with a chamfered surface adapted to engage amating surface on the anvil of the installation tool. The angle of thischamfer will have an effect on the magnitude of the component of theaxial force directed radially inwardly to cause swaging. With thepresent invention, the outer end is tapered to a large diameter and isof a lesser thickness than its beaded counterpart; by selecting thestand-off angle of the chamfer to control the radially inward componentof force, this, in addition to the conical construction, will result ina collar having equal or higher stand-off values than the beaded collar.In this regard it is believed that the conical structure and resultantcircumferential gap require extra energy in swage before the initiationof "primary clinch". It is believed that this combination of factorsassists in resisting the radial inward force component and provides adesired high stand-off.

The collar can be constructed with a straight shank which is radiallyexpanded to the desired conical shape. Where no further thermalprocessing is employed, it is believed that the increase in strength atthe outer end resulting from cold working in this radial expansion stepprovides additional resistance to radially inward deformation. Thus thedesired magnitude of stand-off force will be determined by the balancein hoop strength, resulting from the conical shape and enlarged meandiameter and circumferential gap at the outer end, the selection of theangle of the stand-off chamfer, and, where present, the gradient ofincreasing hardness at the expanded end of the collar. As noted it isbelieved that the conical shape and resultant significant radial gapbetween the inner surface of the collar and pin lock grooves, permits aninitial radially inward deflection, providing energy absorption, whilestill resisting the initial engagement in "primary clinch". In addition,the advantages, previously noted, of uniform fill can be realized.

Since one of the advantages of the novel collar structure, in contrastto a beaded structure, is to provide equal and/or increased pre-loadwhile minimizing distortion of the pin grooves, it can also be usedadvantageously in conjunction with the fit up swage type fasteners asshown in the referenced applications of Dixon and S. M. Sadri. In thisregard the Dixon and Sadri applications are incorporated herein byreference. This is especially true in certain applications, such astruck frames, where it is important that the integrity of the helicallock grooves be maintained such that the swaged collar can be removed byunthreading from the threaded pin.

As noted in the '875 Dixon application, the fit up fastener disclosed isan improvement over conventional threaded fasteners traditionally usedin applications requiring a pre-assembly before final tightening of thefasteners. Thus it is common to secure a structure first by attachingthe associated members with the threaded fasteners loosely engaged ortorqued to be partially tightened. This facilitates adjustment and/oralignment of the structural members to a final, desired orientation evenby partial loosening of the fasteners if necessary. After suchadjustment and/or alignment, the threaded fasteners are tightened to apreselected final torque. Two-piece swage type fasteners are notconfronted with frictional and other problems inherent in threadedfasteners and hence can provide more uniformly predictable clamp loads.However, until the construction shown in the '875 Dixon and Sadriapplications, the swage type fasteners have not been capable ofproviding the initial pre-assembly or clamp up available with threadedfasteners and still provide a full clamp with only a second, finalinstallation step.

In the noted '875 Dixon and Sadri applications, the lock grooves of thepin are in the form of a helical male thread. The collar is providedwith a mating, female thread of a preselected extent such that theinitial pre-assembly or clamp can be accommodated. However, the femalecollar thread is selected to be of a limited circumferential extent andshear strength such that the collar can be brought to its final, desiredclamp position and swaged to the pin via a conventional installationtool. Thus for the final installation, a conventional pull tool can beused to apply a relative axial force between the pin and the collar. Thefemale collar thread is selected such that, in response to the relativeaxial force and at a level prior to the initiation of collar deformationor swaging (primary clinch) into the lock grooves of the pin, it willshear or deform such that the collar will be free to move axially overthe pin and to respond to the installation loads in teh same manner as acollar without such female thread form. Now the workpieces can befinally clamped together with the same effectiveness as typical swagetype fasteners.

In numerous building construction situations, the structure being builtmay be first pre-assembled in one position or location and then erectedor moved to its ultimate position or location where the final assemblytakes place. In such conditions, since these pre-assemblies can be quitelarge, the fasteners can be subjected to separation or handling loads ofsignificant magnitudes. In other applications a high initial clamp loadvia torquing is desirable where the workpieces are fully engaged. Inthose situation, a substantially limited thread may not have sufficientstrength to withstand such loads. In the Sadri application, while alimited thread form is used, the latter conditions are accommodated bythe use of more or higher strength collar threads for engagement withcorresponding pin threads. With more threads or a thread form having ahigher shear strength, however, the attainment of the desired finalclamp load in swage could be inhibited by the resistance of the engagedthread or threads to axial movement of the collar. In addition theworkpieces could be firmly pulled together with no remaining gap andhence no axial movement of the collar would be available whereby thedesired shearing or deformation of the collar threads would beinhibited. To overcome these problems the Sadri collar is provided witha dished flange at its workpiece engaging end. The flange acts as aspring or resistance member such that it will resist high separationloads and/or the torque load for an initial high pre-assembly, pre-loadbut can deflect or collapse upon application of the axial loads inswaging the collar for the final clamp up. Thus the dished flange willpermit axial movement of the threaded portion of the collar such thatthe engaged collar thread or threads have been sheared and/or deformedsufficiently to permit substantially uninhibited transfer of therelative axial force between the pin and collar to provide the desiredfinal clamp load to the workpieces.

However, in order to be able to shear or deform the increased number (orhigher strength) of the engaged threads before swage, the collar must becapable of providing a high stand-off load. This is accomplished by oneform of the present invention.

In some applications it is desirable that the fasteners have a highstrength, high performance characteristic both in clamp up and infatigue. In this latter regard then, it may be advantageous to utilizethe groove shape and concepts of the invention of the '327 and '875applications of Dixon.

Thus, in one form of the present invention, the lock grooves in the pinare very shallow and are constructed to have roots of a simulatedstreamlined shape. The lock grooves are helical and define a desiredthread configuration. The shallow grooves and simulated streamlinedshape, however, provide a resultant fatigue life which is superior tothat of a comparable threaded fastener. Since the preceding constructionis shown and described in the noted applications and since the presentinvention is not restricted to such a construction the details thereof,while incorporated by reference, have been omitted for purposes ofsimplicity.

Thus it is an object of the present invention to provide a novel swagetype fastener utilizing a unique collar construction having highstand-off capabilities and providing generally uniform fill of thelockgrooves of the pin.

It is another object of the present invention to provide a unique collarconstruction for a swage type fastener having high stand-offcapabilities.

It is still another object of the present invention to provide a collarof the above described type which provides a high stand-off capabilitywhile local necking of the pin in the area of swage is inhibited.

It is still another object of the present invention to provide a collarof the above described type which provides a high stand-off capabilitywhile local necking of the pin in the area of swage is inhibited suchthat where the lock grooves are defined by a helical thread form thedistortion of the pin threads will be minimized.

It is another object of the present invention to provide a novel fit upfastener of the above described type utilizing the unique tapered orconical collar having high stand-off capabilities.

It is a general object of the present invention to provide a novel swagetype fastener.

Other objects, features and advantages of the present invention willbecome apparent from the subsequent description and the appended claims,taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of a collar embodying featuresof the present invention;

FIG. 2 is a fragmentary longitudinal sectional view of a prior artcollar utilizing a beaded construction for stand-off;

FIG. 3 is a longitudinal view with some portions shown in section andothers shown broken away of a fastener of the present inventionincluding a pin and a collar similar to that of FIG. 1 but adapted foruse in combination as a swage type fit up fastener and shown in assemblyrelationship with workpieces and with the workpieces being pre-assembledvia torque applied to the fastener to provide an initial clamp load andwith a portion of a pull tool shown as applied to the fastener prior toinitial swage, i.e. primary clinch, of the collar into the lock groovesof the pin;

FIG. 4 is an enlarged sectional view of the fastener of FIG. 3 taken inthe direction of the Arrows 4--4 depicting the fastener with the collarhaving flats to be gripped by a conventional torquing tool (not shown);

FIG. 5 is a longitudinal view similar to that of FIG. 3 depicting thefastener after it has been set;

FIG. 6 is a longitudinal view with some portions shown in section andothers shown broken away of a modified swage type fit up fastener withthe collar including a deformable flange and depicting the fastenerafter it has been torqued to a desired pre-load and with the deformableflange on the collar shown partially deformed to hold workpieces in apre-assembly and with a portion of a pull tool shown as applied to thefastener prior to initial swage, i.e. primary clinch, of the collar intothe lock grooves of the pin; and

FIG. 7 is a view similar to that of FIG. 6 showing the assembly of FIG.6 with the fastener after it has been set with the flange collapsed andcollar swaged onto the pin to provide the desired final clamp load.

Looking now to FIG. 1, a tubular collar 10 for use with a swage typefastener is shown. As will be seen the collar 10 is adapted to be swagedinto locking grooves in an associated pin which is a part of thecombination defining the swage type fastener.

The collar 10 has a shank 12 terminating at its inner end in an enlargedgenerally annular flange 14. The collar 10 has a through bore 15 definedby a first generally straight reduced diameter bore portion 16 locatedat and extending partially beyond the flanged end and an enlargeddiameter generally straight bore portion 18 at its opposite, outer end.An intermediate bore portion 20 is generally frusto-conically shaped andinclines or tapers radially outwardly as it connects the bore portions16 and 18. The collar shank 12 has a generally straight reduced diameterouter surface over a collar portion 22, which is radially in line withthe extended part of reduced diameter bore portion 16 to define agenerally uniform wall thickness t1. The outer surface is then taperedover an intermediate portion 24 and is generally frusto-conically shapedto be generally parallel with the radially inclined intermediate boreportion 20. Over the length of outer surface portion 24, the collarshank 12 has a generally uniform wall thickness t2 which is generallyequal to wall thickness t1.

The outer surface of intermediate portion 24 continues its inclinationgenerally at the same angle over the majority of the surface of an endportion 26. The end portion 26 is coextensive with the straight,enlarged bore portion 18. The outer surface of end portion 26 terminatesin a stand-off chamfer 28 which is inclined at an Angle A relative tothe axis Ax of the through bore 15. The magnitude of radiallycompressive force applied by a swage anvil of an installation tool inswaging the collar 10 onto an associated pin is determined in part bythe angle (A) of the stand-off chamfer 28, which transfers load axiallyand radially for a given applied force via the anvil.

The wall thickness at the outer end portion 26 of collar shank 12 willgenerally increase slightly in thickness from that of t1 and t2 to amaximum thickness t3 at the intersection with stand-off chamfer 28. Theincrease in wall thickness to thickness t3 provides an additional volumeof material; this slight addition in material volume compensates for thecollar material which is forwardly extruded in swage and hence providesfor a more uniform fill of the pin lock grooves throughout the length ofthe swaged portion of collar shank 12."

Thus as noted the collar 10 because of the radially outwardly tapered orconical shape of its shank 12 will provide the desired stand-off but inaddition, because of its generally uniform wall thickness, will providea generally uniform fill of the lock grooves of the associated pin overthe swaged area without excessive necking of the pin and hence withminimal distortion of the lock grooves. The minimization of distortionof the pin grooves is of special importance where they are of a helicalthread form.

A comparison of the structure of the present invention with a collarhaving a prior art beaded construction can be seen from an examinationof FIGS. 1 and 2. In the description of the collar of FIG. 2, portionssimilar to like portions of the collar 10 of FIG. 1 will be given thesame numerical designation with the addition of a postscript "a".

Thus in FIG. 2 the collar 10a has a shank 12a terminating at its innerend in an enlarged flange 14a. The collar 10a has a through bore 15a ofa generally uniform diameter. The collar shank 12a has a generallystraight outer surface portion 22a which, over its length, defines agenerally uniform wall thickness t4. The wall thickness t4 for acomparable fastener application is generally equal to the wall thicknesst1, t2 of the collar of FIG. 1.

The outer surface of the shank portion 12a terminates in an outer endportion 26a having an enlarged circumferential bead 27 which defines awall thickness increasing to a maximum thickness t5 which issubstantially greater than wall thickness t4. The increased thickness t5of the bead 27 extends substantially over the length of outer endportion 26a which terminates in a stand-off chamfer 28a. The chamfer 28ainclines radially at an angle B and serves a purpose similar to that ofchamfer 28.

Thus the prior art construction achieves the required high stand-offstrength by forming a circumferential bead at the top or outer end ofthe collar. This high stand-off strength is due, in part at least, tothe substantial increase in collar material of the bead 27, i.e. definedby thickness t5. As noted the chamfer angle B will effect the magnitudeof radially compressive force resulting from a given axial load appliedby the swage anvil. The chamfer angle B in some cases could be the sameas chamfer angle A for the collar 10 of the present invention.

With a collar 10a of the prior art design the stand-off requirement fora swage type fastener can be met. But the increase in volume of materialat the bead 27 selected to provide the desired stand-off, as noted, cancause high localized necking of the associated pin in the area of swage.

With the frusto-conical collar 10 of the present invention, as shown inFIG. 1, the necessary radially compressive strength or hoop strengthand/or stand-off is achieved while still providing a generally uniformvolume over its swageable length. Thus the tapered collar 10 maintains agenerally constant cross-sectional area along the swage length of thecollar shank 12. In a sense it is a straight tubular shape which has hadits inner and outer diameters expanded radially outwardly.

It is frequently desirable that the volume of collar material in theswage area be selectively greater than the available volume between thepin lock grooves and the cavity of the swage anvil. Where such anoverpack condition is desired, theoretically, the design of the presentinvention will provide a generally uniform percentage of overpack overthe swage length of the collar shank 12.

The present invention is illustrated, by way of example, with a collar10 for a 5/8 inch diameter pin generally having SAE Grade 8 propertieswith the collar 10 generally having around the following dimensions (seeFIG. 1):

1. Diameter of Bore Portion 16=0.630 inches.

2. Diameter of Bore Portion 18=0.730 inches.

3. Maximum Outside Diameter D1 of Shank 12=1.106 inches.

4. Minimum Outside Diameter D2 of Shank 12=0.805 inches.

5. t1=t2=0.175 inches.

6. t3=0.188 inches.

7. L1™1.07 inches.

8. L2=0.400 inches.

9. L3=0.25 inches.

10. L4=0.16 inches.

11. L5=0.29 inches (Flange 14).

12. L6=0.78 inches (Shank 12).

13. L7=0.67 inches (Taper).

14. Chamfer Angle A=25°.

15. Taper Angle C=7°.

16. Radial Gap E=0.05 inches.

17. Radial Pilot Clearance at Bore Portion 16=0.0025 inches.

Thus the maximum volume of collar material represented by the maximumthickness t3 over a finite length of uniform thickness would be around8% greater than that for collar thicknesses t1, t2; the increase in thethickness is gradual up to the maximum thickness t3 which occursessentially at only one point; thus the average increase in volume overthe length L4 is around 4%. Since the length L4 is around 20% of thetotal length L6 of the collar shank 12, the slight increase in volumenoted is gradually distributed over that 20% portion. As noted theresultant slight increase in volume is provided to compensate formaterial which is extruded forwardly during swage and hence assists inproviding uniform fill of the pin lock grooves at the forward or outerend portion 26 of the collar 10.

It will be seen that the inside diameter at outer end portion 26provides a substantial radial clearance with the confronting lock grooveportion of a pin. Thus, when the tapered outer end portion 26 initiallydeflects radially inwardly under load, the radial clearance will permitelastic deflection while precluding premature engagement with the pinlock grooves and hence further assists in providing high stand-offloads. With the collar 10 as noted for use with a 5/8 inch diameter pinthe radial clearance or gap E at the outer end portion 26 will be around0.05 inches or around 8% of the nominal 5/8 inch diameter of thecorresponding pin. Note the radial gap extends over the length L3 whichis approximately around one third (1/3) of the length L6 of the collarshank 12. At the same time the radial clearance with the pin at reduceddiameter bore portion 16 will be around 0.0025 inches whereby the boreportion 16 will act to pilot the collar 10 onto its associated pin. Notethat the radial gap E is provided by a gradually tapering structurewhich extends over a substantial portion (L7) of the length (L6) of thecollar shank 12. Thus the gap E is provided generally without an abruptchange in cross section of the collar shank 12. As indicated, the angleof taper C for the noted fastener was around 7°.

As shown in FIGS. 3 and 4, a modified form of the collar 10 of FIG. 1can be advantageously used in a combination as a fit up fastener. In thedescription of the embodiment for the fit up fastener shown in FIGS. 3and 4 components similar to like components in FIG. 1 will be given thesame numerical designation with the addition of the letter postscript"b".

Looking now to FIGS. 3 and 4, a fastener 30 is shown to include a pinmember 32 and a tubular collar 10b. Pin member 32 has an elongated shank34 which extends through aligned openings 36 and 38 in a pair ofworkpieces 40 and 42, respectively, to be secured together. An enlargedprotruding head 44 at one end of shank 34 engages one side of workpiece40. Adjacent the head 44, the shank 34 has a straight portion 46 whichis adapted to be received within the aligned bores or openings 36 and 38with a clearance fit. Following the straight portion 46 is a lock grooveportion 48 defined by a plurality of grooves 50 having a continuous,helical thread form.

A breakneck groove 52 is located between the lock groove portion 48 anda gripping or pull portion 54 and defines the weakest portion on theshank 34. The pull portion 54 is comprised of a plurality of annularpull grooves 56 which are of a reduced diameter relative to the straightshank portion 46 and the lock groove portion 48. The pull grooves 54 areadapted to be gripped by a tool 58 which is actuable to set the fastener30. The tool 58 can be generally constructed in a manner known to thoseskilled in the art and hence is only partially shown for purposes ofsimplicity. Briefly, the tool 58 has a plurality of jaws 60 adapted togrip the pin member 32 at pull grooves 56. Jaws 60 are located in atubular collet assembly 62 which is slidably supported in an anvilhousing 64 which terminates at one end in a swage anvil 66 having anentry or mouth portion 68.

As shown, the tubular collar 10b has an enlarged flange 14b. Both thepin head 44 and collar flange 14b can be provided with wrenching flatsor irregularities to facilitate gripping by a wrench or other suitabletool for applying a relative torque between the pin member 32 and collar10b. Thus looking now to FIG. 4, the flange 14b can be provided with aplurality of flats 70 to facilitate gripping to a conventional tool orwrench (not shown).

The small diameter bore portion 16b of the collar 10b is of a diameterto be in clearance with the portion of the pin shank 34 extending pastworkpiece 42; a limited female thread 72 is formed at the flange end ofthe bore portion 16b and is adapted to complementarily, threadablyengage the helical lock grooves or threads 50 of pin 32. The shape ofthe collar threads 72 is substantially the same as the shape of the pinthreads 50 for providing good mating engagement. Thus in this case thelatter threaded engagement provides a piloting action for locating thecollar 10b onto the pin 32.

In operation, the workpieces 40 and 42 can be first joined together bythe threaded engagement between the collar thread 72 and the threadedlock grooves 50. The pull portion 54 has a maximum diameter less thanthe inside diameter of the collar thread 72 so that the collar 10b canbe moved onto the pin 32 and collar thread 72 readily applied to thethreaded lock groove portion 48. The number of threads 72 of the collar10b is selected to permit the collar 10b to be torqued to provide adesired pre-assembly, initial clamp force between workpieces 40 and 42and/or to resist anticipated separating or handling forces between theworkpieces 40 and 42.

With this structure, after the torquing and pre-assembly operation, thefastener 30 can now be finally set by the application of a relativeaxial force. Thus after the pre-assembly has been accomplished theinstallation tool 58 is applied to the fastener 30 as shown in FIG. 3and a relative axial force is applied between the pin 32 and collar 10bvia the jaw assembly 60 gripping the pull groove portion 54 and theswage surface of the mouth portion 68 of swage anvil 66 engaging thestand-off chamfer 28b at the outer end of the collar 10b. As therelative axial force increases, the limited collar threads 72 will shearor deform sufficiently to permit the collar shank 12b to move furtheraxially relative to the pin 34. In this condition, however, the swagingor deformation of the material of the collar 10b into the pin lockgrooves 50 has not yet started and, hence, the pin 32 and collar 10b cannow respond as a typical swage type fastener; thus now the workpieces 40and 42 are pulled together at a preselected load by the relative axialforce applied by the installation tool 58 between the pin 32 and collar10b the same as if the collar 10b had not been threadably engaged withthe pin 32, and, as the axial force increases, swaging of the collar 10binto the helical lock groove portion 48 begins. Upon the completion ofswaging and as the axial force continues to increase, a magnitude willbe attained at which the pin 32 will fracture at the breakneck groove 52completing the swaging operation (see FIG. 5). Subsequently, uponfurther actuation of the tool 58, a collar ejector member 74 will beurged forwardly to eject the swaged collar 10b from the anvil 66 thuscompleting the installation.

Thus the workpieces 40 and 42 will be secured together under a finalclamp load substantially the same as if the initial pre-assembly via thethreaded fit up connection had not occurred.

As noted, the enlarged diameter outer portion 26b of tapered collar 10bwill provide stand-off resistance to initial swage, i.e. primary clinch.In this regard, as discussed, the interaction of the swage surface ofmouth portion 68 of the anvil 66 and the angle of the stand-off chamfer28b are such as to assist in providing a preselected stand-off wherebyinitiation of swaging of the collar 10b into the lock grooves 50 willnot begin until that lower magnitude of relative axial force has beenattained which is sufficient to overcome any pre-load from pre-assemblytorque, and to shear or sufficiently deform the limited collar threads72.

As previously indicated, in some building construction applications alimited thread having more or stronger threads than the substantiallylimited thread form shown in the embodiment of FIGS. 3-5 may bedesirable. In these circumstances the dished flange construction shownin the Sadri application could be advantageously utilized in connectionwith the conical or tapered collar construction of the presentinvention. This is shown in the embodiment of FIGS. 6 and 7 wherecomponents similar to like components in the embodiment of FIGS. 3-5have been given the same numerical designation with the addition of theletter postscript "c".

Looking now to FIGS. 6 and 7, a fastener 30c is shown to include a pinmember 32c and tubular collar 10c. Pin member 32c is identical to pinmember 32 of FIGS. 3-5 and hence that description will not be repeated,it being understood that the similarly numbered elements are the same aspreviously described.

Similarly, except for the construction of flange 14c and the use ofthreads 72c which include more threads than threads 72, the tubularcollar 1? c is the same as collar 10b and hence the description of theidentical similarly numbered elements will not be repeated. Looking nowto FIGS. 6 and 7, the flange 14c is dished concavely inwardly apreselected axial distance X from the radially and axially outer end tothe radially and axially inner end. The distance X when the flange 14cis in a relaxed condition is selected to be no less than around one halfthe distance Y which is the pitch of the pin and collar threads 50c and72c, respectively. The relaxed distance X is preferably greater than 1/2Y for purposes to be seen.

In operation, the workpieces 40c and 42c can be first joined together bythe threaded engagement between the collar threads 72c and the threadedlock grooves 50c. Again the pull portion 54c has a maximum diameter lessthan the inside diameter of the collar thread 72c so that the collar 10ccan be moved onto the pin 32c and the collar thread 72c readily appliedto the threaded lock groove portion 48c. The number of threads 72c ofthe collar 10c, while generally limited, is selected to be of sufficientstrength to permit the collar 10c to be torqued to provide a desiredhigh pre-assembly initial clamp force between workpieces 40c and 42cand/or to resist anticipated separating or handling forces between theworkpieces 40c and 42c which are relatively high in magnitude. Thisembodiment of the invention permits an initial clamp force via torquingvarying from a nominal clamp load to a clamp load having a magnitude atwhich the enlarged flange 14c can be deflected to reduce the distance Xto a distance no less than around 1/2 Y. In this manner the workpieces40c and 42c can be selectively clamped or located more or less relativeto each other. Thus additional deflection of the flange 14c of at leastaround 1/2 Y, will still remain available for the swage operation tofollow. This in turn will permit the collar shank 12c to axially move adistance of at least around 1/2 Y during the swage step but prior toinitiation of swage, or initial deformation of the collar 10c into thelock groove portion 48c; thus as the relative axial force in the swageoperation is applied between the pin 32c and collar 10c the collar shank12c in moving at least the distance 1/2 Y will axially override theengaged threads whereby the desired final clamp load can be attained.

The magnitude of applied torque and hence of the initial deflection ofthe flange 14c can be controlled by a suitable torque controlled wrench.To this end suitable wrenching surfaces could be provided on the pinhead44c and/or collar flange 14c. The maximum magnitude of torque applied tothe fastener 30c will be limited such that the initial deflection of theflange 14c will still leave a pre-fastened or pre-clamped distance whichis no less than around one half the thread pitch Y while at the sametime maintaining the integrity of the collar threads 72c.

With this structure, after the torquing operation, the fastener 30c cannow be finally set by the application of a relative axial force. Thusafter the pre-assembly has been accomplished the installation tool 58cis applied to the fastener 30c, as shown in FIG. 6, and a relative axialforce is applied between the pin 32c and collar 10c via the jaws 60cgripping the pull groove portion 54c and the swage anvil 66c engagingthe outer end of the collar 10c. As the relative axial force increases,the collar threads 72c will shear or deform sufficiently to permit thecollar shank 12c to move further axially relative to the pin 32c and tocollapse the flange 14c. Thus where the workpieces 40c and 42c have beenpre-clamped together, via torquing of the fastener 30, and where no gapexists therebetween, the collar flange 14c will collapse as the notedaxial movement of the collar shank 12c occurs permitting the desiredshearing and/or deformation of the collar threads 72c. In thiscondition, however, the swaging or deformation of the material of thecollar 10c into the pin lockgrooves 50c has not yet started and, hence,the pin 32c and collar 10c can now respond as a typical swage typefastener; thus now the workpieces 40c and 42c are pulled together at apreselected load by the relative axial force applied by the installationtool 58c between the pin 32c and collar 10c, the same as if the collar10c had not been threadably engaged with the pin 32c, and, as the axialforce increases, swaging of the collar 10c into the helical lock grooveportion 48c begins. Upon the completion of swaging and as the axialforce continues to increase, a magnitude will be attained at which thepin 10c will fracture at the breakneck groove 52c completing the swagingoperation (see FIG. 7). Subsequently, upon further actuation of the tool58c, the collar ejector member 74c will be urged forwardly to eject theswaged collar 10c from the anvil 66c to complete the installation. Thusthe workpieces 40c and 42c will be secured together under a final clampload substantially the same as if the initial pre-assembly via thethreaded fit up connection had not occurred. Note that as the flange 14ccollapses the reduced diameter bore portion 16c can enlarge, as shown at75 in FIG. 7 whereby disengagement of the threads 72c is furtherassisted.

Similarly as noted with the embodiment of FIGS. 3-5, the enlargeddiameter outer portion 26c of tapered collar 10c will provide stand-offresistance to initial swage, i.e. primary clinch. In this regard, asdiscussed, the interaction between the mouth portion 68c of the anvil66c and the angle of the stand-off chamfer 28c, as noted, are such as toassist in providing a preselected stand-off whereby initiation ofswaging of the collar 10c into the lock grooves 50c will not begin untilthat lower magnitude of relative axial force has been attained which issufficient to overcome any pre-load from pre-assembly torque, and toshear or sufficiently deform the more extensive but still limited collarthreads 72c. Thus the minimum stand-off load capability of the collar10c must be generally equal to the combination or sum of the loadsrequired to overcome any axial pre-load on the fastener 30c, the axialload required to shear or deform the more extensive, but limited collarthreads 72c, and the load required to collapse the dished collar flange14c.

As noted in the Dixon applications and in the embodiment of FIGS. 3-5and FIGS. 6 and 7, the pin 32, 32c can be provided with shallow helicalgrooves with a generally streamlined shape whereby a high strengthconstruction can be achieved having a desirable high clamp load while atthe same time maintaining the integrity of the thread form of the lockgroove portion of the pin whereby torque can be applied for additionalclamp up or collar removal. With the noted shallow groove structure, thevolume of shank 12b, 12c of collar 10b, 10c was selected to generallyprovide `overpacking`, i.e., a volume of material to providesubstantially more volume of collar material for filling pin grooves 50,50c than is available within the swage envelope defined by the cavity ofthe swage anvil 66, 66c and the confronting lock grooves 50, 50c of pin32, 32c. In that construction, it has been found desirable to provide avolume of collar material which has an excess of at least around 14% toaround 16%. Typically the fastener 30, 30c could be constructed ofmaterials generally having the strength characteristics of a Grade 5threaded fastener.

To enhance the strength of fastener 30, 30c the width of the pin grooves50, 50c and adjacent pin shoulders and the complementary grooves andshoulders of the swaged collar 10b can be proportioned in width relativeto the respective shear strengths of the materials of pin 32, 32c andcollar 10b, 10c such that both the shoulders defined by pin grooves 50,50c of the pin 32, 32c and the shoulders defined by interlocking groovesof the swaged collar 10b, 10c are in incipient or simultaneous failurein shear at or above the preselected minimum ultimate design tensileload on associated workpieces 40, 40c and 42, 42c. It is preferred thatthe design provide for the shoulders defined by the grooves of collar10b, 10c to fail prior to the shoulders defined by pin lock grooves 50,50c, , i.e. the shoulders of pin lock grooves 50, 50c would fail inshear at approximately 110% of the tensile load at which the shouldersof collar 10b, 10c would fail. By proportioning the grooves as noted,the engaged length of pin and collar can be minimized for a giventensile load. Of course, by providing sufficient collar length, theabove shear strength relationship can be maintained while providing fora tensile failure diametrically across the pin lock groove portion 48,48c.

Another advantage of employing proportioned strength as noted is thatthe shear strength of the collar threads 72, 72c can be maximizedpermitting the pre-fastened clamp via torquing to be at a relativelyhigh magnitude and/or permitting the fastener 30, 30c in itspre-fastened clamp condition to withstand the necessary loads to holdthe structure together during the fit up operation. This is achieved byvirtue of the fact that the width of collar threads 72, 72c issubstantially the same as the width of the groove of pin threads 50,50c.

With the fastener 30, 30c installed, the swaged collar 10b, 10c willhave a complementary female thread formed in its through bore. This willnow permit the fastener 30, 30c to be removed by torquing the collar10b, 10c off via suitable tools applied to wrenching surfaces on the pinhead 44, 44c and/or the collar flange 14b, 14c.

The fasteners 32, 32c shown and discussed above are shown as pull typefasteners adapted to be finally installed by a conventional pull typetool 58, 58c. The features of the invention, however, are alsoapplicable to a stump type fastener adapted to be finally installed by asqueeze type tool and/or to a pull type fastener having a pin which doesnot have a severable pintail and/or to a pull type blind fastenerutilizing a swageable collar.

Thus when used with a pin in a combination as a fit up fastener thepresent invention provides a unique fastener permitting a variation inclamp load on the workpieces being connected while still permitting ahigh final clamp via a swaged connection between the pin and collar.

The unique construction of the present invention can be used in fastenercombinations other than for fit up fasteners, i.e. blind fasteners, withpins having non-threaded pin grooves. It should also be noted thatcertain pin lock groove constructions may have grooves and crests whichare non-uniform; however, even with this type of groove construction thecollar of the present invention provides for a more uniform fill thanthe beaded prior art construction.

While it will be apparent that the preferred embodiments of theinvention disclosed are well calculated to fulfill the objects abovestated, it will be appreciated that the invention is susceptible tomodification, variation and change without departing from the properscope or fair meaning of the invention.

What is claimed is:
 1. In a fastening system including a fastener forsecuring workpieces together with said fastener adapted to be installedvia a relative axial force applied by an installation tool, saidfastener comprising:a pin having an elongated shank terminating at oneend in an enlarged pin head, a lock groove portion on said shankincluding a plurality of helically extending lock grooves defining athread form, a tubular collar adapted to be located on said pin shankand to be swaged into said lock grooves in response to a firstpreselected magnitude of said relative axial force applicable by theinstallation tool, said collar having a through bore of a diameter togenerally receive said lock grooves in clearance relationship, saidcollar having a female thread formed on said through bore and adapted tothreadably engage said thread form defined by said lock grooves wherebysaid collar can be torqued onto said lock groove portion, said collarthread having a preselected strength selected to deform or shearrelative to said lock grooves in response to a second preselectedmagnitude of said relative axial force applied between said pin and saidcollar by the installation tool with said second preselected magnitudebeing less than said first preselected magnitude, resistance meansassociated with said collar and said pin for permitting the workpiecesto be initially clamped together under a preselected pre-load andthereafter being responsive to said relative axial force to permitrelative axial movement between said collar and said pin of a sufficientaxial distance such that said collar thread will deform or shearrelative to said lock grooves with the movement of said axial distanceand deforming or shearing of said collar thread occurring at adeterminable magnitude of said relative axial force, said firstpreselected magnitude being greater than the combination of saiddeterminable magnitude and said preselected pre-load whereby the finalaxial clamp up load of the workpieces is substantially uninhibited bythe initial threaded engagement of said collar thread and said lockgrooves, said through bore having a reduced diameter bore portion withsaid female thread formed therein whereby said collar is generallythreadably piloted upon said pin shank, said collar having a collarshank portion being generally frusto conically shaped from said reduceddiameter bore portion to an enlarged bore portion at an outer end ofsaid collar, said collar shank portion having a generally uniform wallthickness from said outer end for a distance over its swageable lengthwhereby the frusto conical shape of said collar shank portion provides ahigh hold-off to resist initiation of swage of said outer end of saidcollar into said locking grooves of said pin shank.
 2. The fastener ofclaim 1 with said uniform wall thickness of said collar shank portionproviding for a generally uniform fill of said pin lock groovessubstantially over the swaged portion of said collar shank portion, saiduniform wall thickness of said collar shank portion providingsubstantially minimal distortion of said pin lock grooves.
 3. Thefastener of claim 1 with said collar shank portion tapering at an angleof around 7°.
 4. The fastener of claim 1 with said collar shank portionhaving a slight increase in wall thickness at said outer end.
 5. Thefastener of claim 1 with said collar shank portion having a slightincrease in wall thickness at said outer end generally graduallyincreasing over a distance of approximately around 20% of the length ofsaid collar shank portion.
 6. The fastener of claim 1 with said collarshank portion having a slight increase in wall thickness at said outerend providing a generally distributed increase in volume of collarmaterial at said outer end of around 4%.
 7. The fastener of claim 1 withsaid collar shank portion having a slight increase in wall thickness atsaid outer end providing a generally distributed increase in volume ofcollar material of around 4%, said increase in volume being generallydistributed over a distance of approximately around 20% of the length ofsaid collar shank portion.
 8. The fastener of claim 1 with said collarshank having a hold-off chamfer at said outer end, said hold-off chamferbeing at an angle of around 25% relative to the axis of said collar. 9.In a fastening system including a fastener for securing workpiecestogether with said fastener adapted to be installed via a relative axialforce applied by an installation tool, said fastener comprising:a pinmember having an elongated shank terminating at one end in an enlargedpin head, a lock groove portion on said shank including a plurality ofhelically extending lock grooves defining a thread form, a tubularcollar adapted to be located on said pin shank and to be swaged intosaid lock grooves in response to a first preselected magnitude of saidrelative axial force applicable by the installation tool, said collarhaving a through bore of a diameter to generally receive said lockgrooves in clearance relationship, said collar having a limited femalethread formed on said through bore and adapted to threadably engage saidthread form defined by said lock grooves whereby said collar can betorqued onto said lock groove portion, said limited collar thread havinga preselected strength selected to deform out of said lock grooves inresponse to a second preselected magnitude of said relative axial forceapplied between said pin member and said collar by the installation toolwith said second preselected magnitude being less than said firstpreselected magnitude whereby said collar can be moved axially over saidpin member after deformation of said limited collar thread and prior toinitiation of swaging of said collar into said lock grooves, saidthrough bore having a reduced diameter bore portion with said femalethread formed thereon whereby said collar is generally threadablypiloted upon said pin shank, said collar having a collar shank portionbeing generally frusto conically shaped from said reduced diameter boreportion to an enlarged bore portion at an outer end of said collar, saidcollar shank portion having a generally uniform wall thickness from aidouter end for a distance over its swageable length whereby the frustoconical shape of said collar shank portion provides a high hold-off toresist initiation of swage of said outer end of said collar into saidlocking grooves of said pin shank.
 10. The fastener of claim 9 with saiduniform wall thickness of said collar shank portion providing for agenerally uniform fill of said pin lock grooves substantially over theswaged portion of said collar shank portion, said uniform wall thicknessof said collar shank portion providing substantially minimal distortionof said pin lock grooves.
 11. The fastener of claim 9 with said collarshank portion tapering at an angle of around 7°.
 12. The fastener ofclaim 9 with said collar shank portion having a slight increase in wallthickness at said outer end.
 13. The fastener of claim 9 with saidcollar shank portion having a slight increase in wall thickness at saidouter end generally gradually increasing over a distance ofapproximately around 20% of the length of said collar shank portion. 14.The fastener of claim 9 with said collar shank portion having a slightincrease in wall thickness at said outer end providing a generallydistributed increase in volume of collar material at said outer end ofaround 4%.
 15. The fastener of claim 9 with said collar shank portionhaving a slight increase in wall thickness at said outer end providing agenerally distributed increase in volume of collar material of around4%, said increase in volume being generally distributed over a distanceof approximately around 20% of the length of said collar shank portion.16. The fastener of claim 9 with said collar shank having a hold-offchamfer at said outer end, said hold-off chamfer being at an angle ofaround 25° relative to the axis of said collar.